Supramolecular device

The application of modified electrodes can be exploited in such technologies as energy storage, microelectrochemical devices, supramolecular chemistry, elec-trochromic displays, electrocatalysis, solar energy conversion and electroana-lysis. ... 

Supramolecular chemistry has been a very popular research topic for three decades now. Most applications are foreseen in sensors and opto-electronical devices. Supramolecular catalysis often refers to the combination of a catalyst with a synthetic receptor molecule that preorganizes the substrate-catalyst complex and has also been proposed as an important possible application. The concept, which has proven to be powerful in enzymes, has mainly been demonstrated by chemists that investigated hydrolysis reactions. Zinc and copper in combination with cyclodextrins as the receptor dramatically enhance the rate ofhydrolysis. So far, the ample research devoted to transition metal catalysis has not been extended to supramolecular transition metal catalysis. A rare example of such a supramolecular transition metal catalyst was the results of the joined efforts of the groups of Nolte and Van Leeuwen [SO], They reported a basket-shaped molecule functionalized with a catalytically active rhodium complex that catalyzed hydrogenation reactions according to the principles of enzymes. The system showed substrate selectivity, Michaelis Menten kinetics and rate enhancement by cooperative binding of substrate molecules. The hydroformylation of allyl catachol substrates resulted in a complex mixture of products. 

The book draws on an interdisciplinary panel of experts at the frontiers of research to explore non-linear regulation mechanisms useful for controlling the functions of artificial supramolecules. It begins with a discussion of the synergistic and cooperative events in the formation of supramolecular architectures. It then tackles the synergistic and cooperative control of their properties and functions in supramolecular sensors and devices, supramolecular catalysts, and supramolecular functional assemblies and polymers. 

Given the actual scenario, one can state that the emerging field of nanotechnology represents new effort to exploit new materials as well as new technologies in the development of efficient and low-cost solar cells. In fact, the technological capabilities to manipulate matter under controlled conditions in order to assemble complex supramolecular structures within the range of 100 nm could lead to innovative devices (nano-devices) based on unconventional photovoltaic materials, namely, conducting polymers, fuUerenes, biopolymers (photosensitive proteins), and related composites. 

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

These results have demonstrated that the biomimetic approach of copying the supramolecular principle of archaeal cell envelopes opens new possibilities for exploiting functional hpid membranes at meso- and macroscopic scales. Moreover, this technology has the potential to initiate a broad spectrum of developments in such areas as sensor technology, diagnostics, biotechnology, and electronic or optical devices. 

Finally, to produce the structural and functional devices of the cell, polypeptides are synthesized by ribosomal translation of the mRNA. The supramolecular complex of the E. coli ribosome consists of 52 protein and three RNA molecules. The power of programmed molecular recognition is impressively demonstrated by the fact that aU of the individual 55 ribosomal building blocks spontaneously assemble to form the functional supramolecular complex by means of noncovalent interactions. The ribosome contains two subunits, the 308 subunit, with a molecular weight of about 930 kDa, and the 1590-kDa 50S subunit, forming particles of about 25-nm diameter. The resolution of the well-defined three-dimensional structure of the ribosome and the exact topographical constitution of its components are still under active investigation. Nevertheless, the localization of the multiple enzymatic domains, e.g., the peptidyl transferase, are well known, and thus the fundamental functions of the entire supramolecular machine is understood [24]. 

The use of DNA hybridization just described opens up a novel, uncomplicated, yet powerful strategy for supramolecular synthesis Many different devices are connected to a distinct sequence codon and are subsequently organized on a suitable template strand. The utilization of appropriate nucleic acid scaffolds should even allow the fabrication of highly complex supramolecular structures by means of a modular construction kit. For approximately 20 years, the work of Seeman and coworkers [8,27] have been engaged in the rational construction of ID, 2D, and 3D DNA frameworks. They use branched DNA... 

The nanostructured molecular arrangements from DNA developed by Seeman may find applications as biological encapsulation and drug-delivery systems, as artificial multienzymes, or as scaffolds for the self-assembling nanoscale fabrication of technical elements. Moreover, DNA-protein conjugates may be anticipated as versatile building blocks in the fabrication of multifunctional supramolecular devices and also as highly functional-... 

Acknowledgements. This work has been supported by MIUR (Supramolecular Devices Project), University of Bologna (Funds for Selected Topics), and EC (HPRN-CT-2000-00029). C.S. acknowledges the Swiss National Science Foundation for financial support. 

Lehn JM. 1988. Supramolecular chemistry—Scope and perspectives molecules, supermolecules, and molecular devices. Angewandte Chemie—International Edition in English 27(1) 89-112. 

Hirst, A.R., Escuder, B. and Miravet, J.F. and Smith, D.K. (2008) High-tech applications of self-assembling supramolecular nanostructured gel-phase materials from regenerative medicine to electronic devices. Angewandte Chemie International Edition, 47 (42), 8002-8018. 

Balzani V, Scandola F (1996) Photochemical and photophysical devices. In Reinhoudt DN (ed) Comprehensive supramolecular chemistry, vol 10. Elsevier Science, Oxford, p 687... 

Successive H-bond urea self-assembly of 4 and sol-gel transcription steps yield preferential conduction pathways within the hybrid membrane materials. Crystallographic, microscopic and transport data confirm the formation of self-organized molecular channels transcribed in solid dense thin-layer membranes. The ionic transport across the organized domains illustrates the power of the supramolecular approach for the design of continual hydrophilic transport devices in hybrid membrane materials by self-organization (Figure 10.8) [42-44]. 

Controlled formation of three-dimensional functional devices in silica makes the hybrid membrane materials presented here of interest for the development of a new supramolecular approach to nanoscience and nanotechnology through self-organization, towards systems of increasing behavioral and functional addressabilities (catalysis, optical and electronic applications, etc.). 

Hybrid supramolecular dynamic membranes as selective information transfer devices. Desalination, 199, 521-522. 

A methanofullerene derivative possessing an ammonium subunit has been prepared and subsequently shown to form a supramolecular complex with a porphyrin-crown ether conjugate <06T1979>. The synthesis and study of these fullerene-containing supramolecular photoactive devices have also been reported <06CRC1022>. 

Figure 8.18 TbPc2-based molecular spin-tronic devices, (a) Graphene nanotransistor with sensitivity at the single-molecule level [39, 256], (b) Scheme of the supramolecular spin valve architecture [217]. (c) Scheme of the carbon nanotube NEMS. The magnetization reversal of a TbPc 2 SIMM from a spin state Jz = +6 to Jz = -6 results in a rotation...

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